The swiftly burgeoning learn of the earlier 20 years on agonist-antagonist analgesics and opioid receptors makes this exhaustive overview of opioid anal­ gesics rather correct and well timed. After an introductory bankruptcy the extra 12 chapters commence logically with morphine and congeners (4- epoxymorphinans) and finish with opioid receptors.

T. J. Mu¨ller 28 1 Introduction Heterocycles are ubiquitous in all aspects of modern chemistry, such as medicinal chemistry, bioorganic and bioinorganic chemistry, and materials sciences. Their facile preparation has remained among of the most challenging goals for synthetic chemistry. However, addressing issues like simplicity, safety, brevity, selectivity, yield, environmental demands, availability of starting materials, and diversity all at the same time in the sense of an ideal synthesis [1] is an endeavor almost like squaring the circle (Fig.